多铁性复合薄膜的制备及性能研究

发布时间：2018-11-22 09:20

【摘要】：磁电材料是一种集多种磁性能于一体的材料,不仅具有铁电、铁磁等铁性能,而且这些铁性能通过相互间的耦合,产生新的性能。比如铁电与铁磁间通过有序参量的耦合作用产生一种新的“磁电效应”。因这些材料在器件领域独特的应用价值,正吸引越来越多人的研究。本文主要通过凝胶-凝胶法、脉冲激光沉积法(PLD)和磁控溅射法(MS)制备了BaTiO3(BTO)/CoFe2O4(CFO)/SrRuO3(SRO)和BTO/CFO/Ta2O5/SRO的磁电复合薄膜,并对其结构和性能进行了研究。首先采用溶胶-凝胶法制备了BTO单层薄膜,该BTO薄膜具有良好铁电-光学性能,是良好的绝缘材料,电阻值约为1x1014?/cm。薄膜中存在可见光波段强烈的光致发光(PL)效应。薄膜PL谱的理论和实验结果表明,禁带间存在直接受有序-无序度影响的局域态。BTO薄膜的紫外-可见吸收光谱表明BTO薄膜是直接禁带材料,禁带宽带约为3.02 eV。用溶胶-凝胶法制备均匀性好,致密度高,各组分相纯的BTO、CFO陶瓷材料作为PLD制备复合薄膜的靶材。在(?00)取向的单晶SrTiO3(STO)上制备的CFO/BTO/SRO、CFO/BTO/Ta2O5/SRO复合薄膜质量良好,除了Ta2O5为非晶态,SRO、BTO、CFO均沿衬底(?00)方向择优取向。CFO/BTO/SRO、CFO/BTO/Ta2O5/SRO复合薄膜均表现出良好的铁电性,前者铁电性弱于后者,两者饱和极化强度分别37.3μC/cm-2和47.6μC/cm-2,说明缓冲层Ta2O5的能抑制BTO和SRO间的界面效应,提高复合薄膜铁电性能。两种复合薄膜磁性能相差不大,饱和磁化强度分别为130 emu/cm3和127 emu/cm3。从理论上分析计算了复合薄膜磁电耦合系数,在不考虑衬底夹持效应的情况下E31?=923 mv/cm-1Oe-1,考虑衬底夹持效应E31?极小。实验测试CFO/BTO/SRO、CFO/BTO/Ta2O5/SRO复合薄膜磁电耦合系数分别为1E31? = 88 mv/ cm-1,2E31?=130 mv/cm-1Oe-1。说明高介电的Ta2O5缓冲层能通过抑制界面效应来提高复合薄膜铁电性和减小衬底夹持作用,进而提高复合薄膜的磁电耦合性能。
[Abstract]:Magnetoelectric material is a kind of material which integrates many kinds of magnetic properties. It not only has ferroelectric, ferromagnetic and other iron properties, but also produces new properties by coupling with each other. For example, a new "magnetoelectric effect" is produced by the coupling of ordered parameters between ferroelectricity and ferromagnetism. Because of their unique application value in the field of devices, these materials are attracting more and more research. In this paper, BaTiO3 (BTO) / CoFe2O4 (CFO) / SrRuO3 (SRO) and BTO/CFO/Ta2O5/SRO magnetoelectric composite films were prepared by gel-gel method, pulsed laser deposition method (PLD) and magnetron sputtering method (MS). Its structure and properties are also studied. Firstly, BTO monolayer thin films were prepared by sol-gel method. The BTO thin film has good ferroelectric-optical properties and is a good insulating material with a resistance value of about 1 x 1014 / cm ~ (-1). There is a strong photoluminescence (PL) effect in the visible band in the thin films. The theoretical and experimental results of PL spectra show that there are local states directly affected by the degree of order-disorder between the bandgap. The UV-Vis absorption spectra of BTO films indicate that the BTO films are direct bandgap materials, and the bandgap band gap is about 3.02 eV.. BTO,CFO ceramic materials with good homogeneity, high density and pure components were prepared by sol-gel method as targets for the preparation of composite films by PLD. The quality of CFO/BTO/SRO,CFO/BTO/Ta2O5/SRO composite films prepared on (? 00) oriented single crystal SrTiO3 (STO) is good, except that Ta2O5 is amorphous, and SRO,BTO,CFO is oriented in the direction of substrate (? 00). CFO/BTO/SRO, The CFO/BTO/Ta2O5/SRO composite films showed good ferroelectric properties, the former was weaker than the latter, and the saturation polarization of the two films was 37.3 渭 C/cm-2 and 47.6 渭 C / cm-2, respectively. The results show that the buffer layer Ta2O5 can inhibit the interfacial effect between BTO and SRO and improve the ferroelectric properties of the composite film. The magnetic properties of the two kinds of composite films have little difference. The saturation magnetization is 130 emu/cm3 and 127 emu/cm3., respectively. The magnetoelectric coupling coefficient of the composite thin film is calculated theoretically. The substrate clamping effect is considered in E31N 923 mv/cm-1Oe-1, without considering the substrate clamping effect. Very small. The magnetoelectric coupling coefficients of CFO/BTO/SRO,CFO/BTO/Ta2O5/SRO composite films were measured to be 1E31? = 88 mv/ cm-1,2E31?=130 mv/cm-1Oe-1., respectively. It is shown that the high dielectric Ta2O5 buffer layer can improve the ferroelectric properties of the composite thin films and reduce the substrate clamping by suppressing the interface effect, thus improving the magnetoelectric coupling performance of the composite films.
【学位授予单位】：贵州大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.2

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